real function esum()
      include 'esum.inc'
      real diff,sum
      real sx0(4),sp0(4)
      common /sumc/diff,sum,sx0,sp0
      data diff,sum/0,0/
      diff=0
      if (xin(4).eq.0) then
        print *, 'cant call esum twice, joker'
      endif
      do i=1,3
        diff=diff+(xin(i)-sx0(i))**2
        diff=diff+(pin(i)-sp0(i))**2
        sx0(i)=xout(i)
        sp0(i)=pout(i)
      enddo
      if (diff.lt.10) then
        sum=sum+desum
        esum=-1
      else
        esum=sum
        sum=desum
      endif
      xin(4)=0
      end